This invention relates to electrical signal connectors and in particular to an improved connector for handling very high speed signals, having very high interconnect bandwidths and ultra high signal densities.
Present high-bandwidth packaging designs for very high speed integrated circuits (VHSIC) and other technologies comprise the use of a double sided module assembly with printed wiring boards (PWBs) bonded to opposite sides of a central heat frame. The use of a double sided module assembly and the need for high packaging density necessitates a surface mount approach to PWB construction. Existing surface mountable connector systems, especially from military application suppliers for FORMAT-E modules defined in the Navy Standard Hardware Acquisition and Reliablility Program (SHARP), are limited to 304 I/0 pins; however, the number of pins available per PWB is exactly one-half of this number, since one-half of the pins must be dedicated to each PWB and pins are not typically shared between PWBs. In addition, a considerable number of pins (25 to 30) are required to bring power to the module assembly while a greater number (50 to 60) are required to insure a good low impedance ground connection for the module assembly due to the high switching currents, the large number of I/0 signals, and the use of high speed integrated circuit technologies. This results in a large reduction in the number of pins actually available for I/0 signal usage. Signal interconnections on and off the module assembly are accomplished using blade and tuning fork, pin and socket or other friction type contact interfaces with a best-case pad pitch of 40 mils, resulting in an I/0 density of 25/inch and a connector contact count in the 100 to 300 range.
Another type of connector assembly is shown in a patent to Norbert L. Moulin, U.S. Pat. No. 4,453,795, "Cable-to-Cable/Component Electrical Pressure Wafer Connector Assembly," assigned to Hughes Aircraft Co., El Segundo, CA. Moulin describes an approach of making interconnections without the use of conventional frictionally engaging electrical connectors. Instead, for terminating at least 2 cables, or one cable to one component which have identical configurations, metallic buttons are formed on the contact pads of one termination so that when the terminations are placed opposing each other and pressed between two pressure plates or surfaces, connections are made between the respective contact pads of the terminations by means of the buttons. Further, placed between the pressure surfaces is a compression pad of elastomeric material which may be confined or unconfined, as desired. If not confined, the compression pad acts as both the means for evenly distributing the pressure between the terminations and to afford a gas-tight contact therebetween without deforming the buttons beyond their elastic limit. When confined, a spring relief is additionally included to control the force of pressure so as to permit a larger pressure to be exerted between the pads when a large number of contacts or buttons are utilized. This approach reduces the area required for each signal when applied to a connector assembly, thereby supporting gains made by increasing packaging density within a module assembly.
However, next generation packaging for advanced VHSIC and other high speed technology applications will have to accommodate higher clock rates, higher interconnect bandwidths, and I/0 signal density approaching 50/inch requiring connector contact counts in the 400 to 500 range.